Theoretical study on the mechanism and kinetics of the formation β-carotene epoxides from the oxidative degradation of β-carotene

Some factors such as oxidation can significantly affect the level of β-carotene after processing and during the storage of foods. Oxidative degradation of β-carotene with the active forms of oxygen produces β-carotene 5,6 and 5,8-epoxides. Two mechanisms involving a direct attack on the double bonds of the β-carotene by 1O2 (a neutral mechanism) and 3O2 (a radical mechanism) oxygen have been proposed and considered kinetically and thermodynamically by the density functional theory method. It concluded that due to the smaller energy barrier in the first step, the neutral mechanism with 1O2 is a more desirable path than the diradical mechanism with 3O2 and this was in complete agreement with the experimental reality of more reactivity of 1O2. The energy barriers of the stepwise manner in the intersystem crossing pathway showed a more favorable pathway in the neutral mechanism. The deviation of spin contamination values was ignorable in the diradical mechanism.